Electric discharge machining condition setting system

ABSTRACT

A wire cut electric discharge machining condition setting system including cursor shift push button switches for selecting with a cursor one of the machining conditions displayed on a screen at a CRT display unit, numerical push button switches for setting values of the selected machining conditions, and increment and decrement push button switches for continuously updating the preset values of the machining conditions all arranged in a wire cut electric discharge machine. The value of the machining condition selected with the cursor is set by the numerical push button switches and is updated by the increment and decrement push button switches.

BACKGROUND OF THE INVENTION

The present invention relates to a machining condition setting system ina wire cut electric discharge machine having a numerical control unit.

In conventional wire cut electric discharge machines, a predeterminedvoltage is applied to a gap formed between a workpiece and a wireelectrode extending along the longitudinal direction of the machine inorder to cut the workpiece by a small amount each time. At the sametime, the wire electrode is moved relative to the workpiece inaccordance with instruction data so as to produce a workpiece with apredetermined shape. An electric discharge machine of this type requiresspecific machining conditions such as a voltage applied to the gap, apeak value and an average value of a current which flows through thegap, a capacitance of a discharge circuit, a duty cycle of a pulseapplied to the gap, a tension force acting on the wire electrode, and aresistivity of a working fluid supplied to the gap, depending on thematerial and thickness of the workpiece and a diameter of the wireelectrode. An operator who operates the wire cut electric dischargemachine must preset these machining conditions at an operation panel onthe numerical control unit by considering the material and thickness ofthe workpiece and the diameter of the wire electrode.

However, in the conventional wire cut electric discharge machine, themachining conditions are preset by a rotary switch. For this reason,rotary switches must be provided for the respective machiningconditions. When the preset values of the machining conditions areupdated, it is difficult to gradually update these preset values. Inaddition to this disadvantage, when the preset values of the machiningconditions change greatly during machining, hunting occurs and the wireelectrode is undesirably cut. As a result, scratches are formed on theworkpiece.

SUMMARY OF THE INVENTION

It is a first object of the present invention to display variousmachining conditions on a CRT display unit so as to allow values ofthese machining conditions to be set with numerical push buttons.

It is a second object of the present invention to provide an electricdischarge machining condition setting system capable of continuouslyupdating the preset data.

It is a third object of the present invention to provide an electricdischarge machining condition setting system capable of changing a dataupdating rate in accordance with a degree of updating when the variousmachining conditions are continuously updated.

In order to achieve the above objects of the present invention, variousmachining conditions are displayed on a screen at a CRT display unit ina wire cut electric discharge machine to allow an operator to selectproper machining conditions with a cursor and preset values withmachining condition push buttons. In addition to this arrangement, thereare also provided increment and decrement push buttons in addition tonumerical push buttons "0" to "9" to allow continuous increase/decreaseof the preset values by depressing the increment/decrement push buttonfor a given time.

According to the present invention, by changing the depression time ofthe increment/decrement push button, a data updating rate can bechanged.

As described above, in a wire cut electric discharge machining settingsystem, the machining conditions can be easily preset and updated withnumerical push buttons. In addition to this advantage, the preset valuescan be continuously changed by using the increment and decrement pushbuttons. As a result, hunting and wire disconnections will not occureven if the preset values are greatly changed, unlike in conventionalupdating using rotary switches.

When the preset values are gradually updated, the updating rate can bechanged by changing the depression time of the increment/decrement pushbutton, thereby accurately updating the preset data at a high speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of the present invention;

FIG. 2 is a graph illustrating the operation of the FIG. 1 embodiment;and

FIG. 3 is a flow chart illustrating the operation of the FIG. 1embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described in detail with reference to theaccompanying drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.Referring to FIG. 1, reference numeral 1 denotes a wire cut electricdischarge machine; reference numeral 2 denotes a CPU; reference numeral3 denotes an operation panel; and reference numeral 4 denotes pushbutton switches. The push button switches 4 comprise numerical pushbutton switches K0 to K9 which respectively correspond to "0" to "9"keys, cursor shift button switches 6 and 7 for shifting a cursor Cappearing on a screen at a CRT display unit 5, an increment push buttonswitch 8 for increasing a preset value, and a decrement push buttonswitch 9 for decreasing the preset value.

When various machining conditions 10 are preset and updated, theoperator selectively depresses the cursor shift button switches 6 and 7to vertically shift the cursor C so as to select a desired one of themachining conditions 10. The operator selectively depresses thenumerical push button switches K0 to K9 to enter a desired value. Forexample, as shown in FIG. 1, machining condition "VOLTAGE" is selectedwith the cursor C, and numerical push button switches K1 and K5 aredepressed to enter numerical data "15". In this manner, the machiningconditions 10 can be easily preset with the push button switches.

However, when the preset values are updated during machining, huntingand wire disconnection occur. In particular, the current abruptlyincreases and the wire electrode tends to be disconnected. In order toprevent these drawbacks, according to the present invention, theincrement and decrement push buttons 8 and 9 are arranged tocontinuously and gradually update the preset values. In particular, whenthe increment (+) push button switch 8 is continuously depressed, thevalue of the selected machining condition is incremented one by one.Similarly, when the decrement (-) push button switch 9 is continuouslydepressed, the value of the selected machining condition is decrementedone by one. In this manner, the preset value can be continuouslychanged.

The effect of gradual updating of the preset data will be described withreference to FIGS. 2 and 3. Referring to FIG. 2, a depression time t ofthe increment/decrement push button switch 8 or 9 is plotted alng theabscissa, and a change V in preset value of each machining condition 10is plotted along the ordinate. It should be noted that FIG. 2 shows thecase wherein the increment push button switch 8 is depressed to increasethe value of a machining condition 10. When the operator continuouslydepresses the increment push button switch 8 within a firstpredetermined time T1 (e.g., one second), the value of the selectedmachining condition is incremented by one, as shown in FIG. 2. However,when the operator continuously depresses the increment push buttonswitch 8 for longer than the first predetermined time T1, the value ofthe selected machining condition is incremented one by one for each of athird predetermined time T3 (e.g., 0.5 second). In addition, if theoperator continues to depress the increment push button switch 8 formore than a second predetermined time T2 (e.g., three seconds), thevalue of the selected machining condition is incremented by one for eachof a fourth predetermined time T4 (i.e., 0.3 second) which is shorterthan the third predetermined time T3. FIG. 2 shows the case wherein theincrement push button switch 8 is continuously depressed, as previouslymentioned. However, when the decrement push button switch 9 iscontinuously depressed, the value is decreased in the same manner asthat described with reference to the increment push button switch 8.Thus, the data updating rate is changed in accordance with thedepression time of the increment/decrement push button switch 8 or 9,thereby enabling a desired value to be quickly selected.

The operation for increasing the preset value will be described withreference to the flow chart shown in FIG. 3. The CPU 2 checks in step S1if both the increment and decrement push button switches 8 and 9 are ONor OFF. If in step S1 they are, then the present machining condition isproduced and displayed on the screen at the CRT display unit 5 in stepS14. Subsequently, the operator selectively depresses the cursor shiftbutton switches 6 and 7 to shift the cursor C to the position of adesired machining condition whose data is to be updated. When theoperator then depresses the increment push button switch 8, the CPU 2detects in step S1 that either the increment button switch 8 or thedecrement button 9 (increment button switch in the case as shown in FIG.2) is depressed. The CPU 2 then checks in step S2 whether or not the"ON" button (increment button) was ON during the previous clock time.Since this button was not turned on in the previous clock time, countersA and B in the CPU 2 are cleared such that A=0 and B=0 in steps S4 andS10. Since the depressed button is the increment push button switch 8(step S11), the value of the machining condition indicated by the cursorC is increased by one in step S12. The updated machining condition isproduced and displayed at the CRT display unit in step S14. When thenext clock signal is entered, the increment push button switch 8 is setin the ON state (step S1). In particular, since the increment pushbutton switch 8 was turned on during the previous clock signal and isstill ON (step S2), the counters A and B are respectively incremented byone in steps S3 and S5. In step S6 the count of the counter A iscompared with the first predetermined time T1 to determine if the countis smaller than the value of the first predetermined time T1. If it is,then steps S1, S2, S3, S5 and S6 are repeated for every clock pulse soas to increment the counters A and B. More specifically, as shown inFIG. 2, the incremented value is maintained until the firstpredetermined time T1 has elapsed. When it is determined in step S6 thatthe count of the counter A exceeds the first predetermined time T1, thenthe count of the counter A is compared with the second predeterminedtime T2 in step S7 to determine if the count is smaller than the secondpredetermined time T2. If if is, then the count of the counter B iscompared with the third predetermined time T3 in step S8 to determine ifthe count is smaller than the time T3. Initially, the count of thecounter B is larger than the value of the third predetermined time T3,so that the counter B is cleared in step S10. The value of the selectedmachining condition is incremented by one in step S12 and theincremented value is displayed in step S14. During the subsequent clocktimes, steps S1, S2, S3, S5, S6, S7 and S8 are repeated until the countof the counter B exceeds the third predetermined time T3. When the countof the counter B becomes equal to or larger than the value of the thirdpredetermined time T3 (i.e., if NO condition exists in step S8), thecounter B is cleared in step S10. The value of the selected machiningcondition is incremented by one in step S12. The updated value isdisplayed in step S14. In the same manner as described above, theoperation is repeated until the count of the counter A exceeds the valueof the second predetermined time T2. As shown in FIG. 2, the value ofthe selected machining condition is incremented one by one for eachinterval corresponding the third predetermined time T3, during intervalbetween the first predetermined time T1 and the second predeterminedtime T2. When it is determined in step S7 that the count of the counterA exceeds the value of the second predetermined time T2, the count ofthe counter B is compared with a fourth predetermined time T4 in step S9to determine if the counter is smaller than the value of the fourthpredetermined time T4. If it is, then the value of the machiningcondition is not updated. However, if is not, then the counter B is setto be zero in step S10, and the value of the machining condition isincremented by one. Thereafter, every time the count of the counter Bexceeds the value of the fourth predetermined time T4, the value of themachining condition is incremented by one. In this case, the fourthpredetermined time T4 is set to be shorter than the third predeterminedtime T3 and the updating rate is increased. In other words, when thedepression time is elongated, the updating rate is increased.

The operator depresses the decrement push button switch 9 to decreasethe value of the machining condition in the same manner as describedwith reference to the operation of the increment push button switch 8.

In the above embodiment, a two-step updating rate is adopted to changethe values of the machining conditions. However, three- or four-stepupdating rates can be used in place of the two-step updating rate.

We claim:
 1. A wire cut electric discharge machining condition settingsystem comprising:a display unit; cursor shift push button switch meansfor shifting a cursor on the display unit and for selecting, via saidcursor, a machining condition to be changed; numerical push buttonswitch means for receiving manual inputs and for changing the selectedmachining condition in accordance with said manual inputs; increment anddecrement push button switch means including an increment button and adecrement button, for updating a preset value of said selected machiningcondition, includingmeans for determining whether or not the incrementbutton is depressed and for determining whether or not the decrementbutton is depressed; means for increasing the preset value by apredetermined amount in accordance with the increment button beingdepressed; means for decreasing the preset value by a predeterminedamount in accordance with the decrement button being depressed; meansfor changing the rate at which said selected machining condition ischanged in accordance with a depression time of said increment anddecrement push button switch means and such that the preset value ischanged so that neither hunting nor undesirable cutting of the wireelectrode occurs when the preset value is updated during machining,includingmeans for detecting the time that said increment and decrementpush button switch means is depressed; means for determining if thedetected time falls in a first time period of a second time periodlarger than the first time period; and renewal means for selectivelyoperating said increment and decrement push button switch means for afirst time interval when the detected time falls within the first timeperiod, for operating said increment and decrement push button switchmeans for a second interval when the detected time falls within thesecond time period and for operating said increment and decrement pushbutton switch means during a first time period so as to prevent abruptchanges in the preset value during a time from just after said incrementand decrement push button switch means is depressed to the time at whichsaid first time period begins.
 2. A wire cut electric dischargemachining condition setting system comprising:display means having adisplay screen with a cursor, for displaying a plurality of machiningconditions and associated values; and input means for controlling theposition of the cursor on the display screen, for selecting, inaccordance with the position of the cursor, a machining condition havingone of an associated value to be changed and a preset value, and forinputting data corresponding to an amount of change in the associatedvalue of the selected machining condition such that the associated valueis continuously changed by a predetermined amount for first intervalsduring a first time period and by a predetermined amount for secondintervals being less than the first intervals, during a second timeperiod and such that the preset value is changed so that neither huntingnor undesirable cutting of the wire electrode occurs when the presetvalue is updated during machining.